Environmental sustainability is an ideal which is gaining momentum within the construction industry. Engineers are making great strides towards increased environmental sustainability by updating processes, improving designs and selecting greener materials. These changes are a response to the desires of building owners and operators, as well as those who work and dwell within those buildings. Contractors are realizing that higher performing buildings and infrastructure are required in order to remain competitive. Producers of pre-cast concrete construction materials have raised the performance of their product since the 1940s by finding and exploiting niche benefits that are unique to pre-cast concrete construction. These advances have included developing durable finishes, superior insulative properties in multi-wythe wall components, economy with formwork, rapid constructability and many others. However, the industry must address the greenhouse gas emissions associated with Portland cement, and further integrate the benefits of concrete materials into building functions and operation.
Maintaining acceptable temperatures in buildings (by heating and cooling) accounts for a large proportion of global energy consumption. Thermal insulation in buildings is an important factor to achieving thermal comfort for its occupants. Insulation reduces unwanted heat loss or gain and can decrease the energy demands of heating and cooling systems. Building insulations also commonly use the principle of small trapped air-cells (e.g. fiberglass, cellulose, rock wool, polystyrene foam, urethane foam, vermiculite, perlite, cork, etc.). A well-insulated building is energy-efficient, thus saving the owner money and provides more uniform temperatures throughout the interior space. There is less temperature gradient both vertically (between ankle height and head height) and horizontally from exterior walls, ceilings and windows to the interior walls, thus producing a more comfortable occupant environment when outside temperatures are extremely cold or hot. A well-insulated budding also has minimal recurring expense. Unlike heating and cooling equipment, insulation is designed to be permanent and thus does not require maintenance, upkeep, or adjustment. Insulation helps to lower the carbon footprint required to construct, heat and cool the house.
Another factor which affects a structure's carbon footprint is its thermal mass. In building design, thermal mass is a property of the mass of a building which enables it to store heat, providing “inertia” against temperature fluctuations. For example, when outside temperatures are fluctuating throughout the day, a large thermal mass within the insulated portion of a house can serve to “flatten out” the daily temperature fluctuations, since the thermal mass will absorb thermal energy when the surroundings are higher in temperature than the mass, and give thermal energy back when the surroundings are cooler, without reaching thermal equilibrium. This is distinct from a material's insulation value, which reduces a building's thermal conductivity, allowing it to be heated or cooled relatively separate from the outside, or even just retain the occupants' thermal energy longer. Thermal mass is a term well known in the art and helps to describe an adobe building's ability to avoid temperature fluctuations throughout the day and night even when the outside temperature rises and falls.
In the early part of the twentieth century, most homes in the United States were constructed with little to no thought of energy efficiency or insulation. This was especially true in the northern regions, but less so in the desert southwest. One popular building material in the deserts is adobe due to its thermal mass. An adobe brick is a composite material made of clay mixed with water and an organic material such as straw or dung. The soil composition typically contains clay and sand. Straw is useful in binding the brick together and allowing the brick to dry evenly, thereby preventing cracking due to uneven shrinkage rates through the brick. Adobe can serve as a significant heat reservoir due to the thermal properties inherent in the massive walls typical in adobe construction. In climates typified by hot days and cool nights, the high thermal mass of adobe averages out the high and low temperatures of the day, moderating the living space temperature. The massive walls require a large and relatively long input of heat from the sun and from the surrounding aft before they warm through to the interior. After the sun sets and the temperature drops, the warm wall will then continue to transfer heat to the interior for several hours due to the time lag effect. Thus, a well-planned adobe wall of the appropriate thickness is very effective at controlling inside temperature through the wide daily fluctuations typical of desert climates, a factor which has contributed to its longevity as a building material.
A need exists to devise a building structure system which decreases the carbon footprint of both the building materials used to create the structure and the carbon footprint to maintain the comfort of the individuals within that structure.